Electric stimulation rehabilitation or electrotherapy had been discovered way back in 400 BC with the help of a torpedo fish that produces an electric shock reaching up to 150 volts. People used to take these fish from streams and they place them on the body’s painful area and the electricity produced from the fish controlled the pain.
It was when the gate control theory of pain in 1965 that reintroduced electric stimulation rehabilitation after it had lost the interest of many skeptics in the nineteenth century. The theory suggests that when the large nerve fibers activity increases, it tends to close the gate blocking information or signals of pain to the brain.